Even if your phone was unlocked, they probably wouldn't bother more than a cursory glance. They have more phones to steal than to bother with is on some random person's phone. When the data is important, the theft will be more targeted.
I haven't heard of it recently, but a few years ago there was a story on phone operator temporary staff that would offer clients to move their contact info from their old phone to the new one (it's a completely legit service) and keep a backup of the old info to sell it. The price for an entry was something like 2 cents, but data would be sold by batches for about 700~800 dollars.
I didn't find any quick resources in english, just for the numbers there was this piece by trendmicro (to note, they are of course biased to make the number a littre bigger) http://blog.trendmicro.co.jp/archives/4828